By Stephen Beech

Night shift workers can reduce their cancer risk by taking the sleep hormone melatonin, suggests a new study.

Melatonin supplements may help offset cancer-causing DNA damage linked to shift work, say scientists.

It boosts the body’s ability to repair any damage, according to the findings of a small clinical trial.

Canadian researchers say the trial suggests larger studies looking at different doses and the potential long term effects of melatonin supplementation are now warranted.

Previous research has shown that normal night-time production of the body clock hormone, melatonin, is suppressed in night shift workers.

Study author Dr. Parveen Bhatti explained that the suppression compromises the body’s ability to repair oxidative DNA damage, the by-product of normal cellular processes, heightening the risk of certain cancers in shift workers.

The research team wanted to find out if melatonin supplementation might help offset any damage by enhancing DNA repair in 40-night shift workers.

Half the participants were randomly assigned to a daily 3mg melatonin pill taken with food and an hour before going to sleep during the day for four consecutive weeks.

The other half were randomly assigned to a 3mg dummy pill following the same schedule.

All the participants worked a minimum of two consecutive night shifts every week, of at least seven hours per night, for at least 6 months. None had any sleep disorders or long term conditions.

Urine specimens were collected during the second of two subsequent day sleep and night shift periods, once before starting the trial and once near the end of the four weeks.

Participants wore activity trackers to measure how long they slept during the day.

Levels of 8-OHdG, an indicator of DNA damage repair capacity, were measured in all urine passed during periods of daytime sleep and the subsequent night shift.

The findings, published online by the journal Occupational and Environmental Medicine, showed urinary levels of 8-OH-dG were 80% higher during daytime sleep – indicating better repair – among those taking the melatonin supplement than those taking the dummy pill.

However, there was no significant difference in urinary 8-OH-dG levels during the subsequent night shift.

Dr. Bhatti said: “Increased oxidative DNA damage due to diminished DNA repair capacity is a compelling mechanism that may contribute to the carcinogenicity of night shift work.

“Our randomized placebo-controlled trial suggested melatonin supplementation may improve oxidative DNA damage repair capacity among night shift workers.

“Our findings warrant future larger-scale studies that examine varying doses of melatonin supplements and longer-term impacts of melatonin use.

“Pending the outcome of such studies, melatonin supplementation may prove to be a viable intervention strategy to reduce the burden of cancer among night shift workers.”

He added: “Assessing long-term efficacy is critical since those who work night shifts for many years would need to consistently consume melatonin supplements over that time frame to maximize the potential cancer prevention benefits.”